Transmitters have revolutionized biologists' understanding of both terrestrial and aquatic animal movements since they were first attached to animals about 50 years ago. Accurate information on fish movement, for example, is needed to understand the impacts of hydroelectric dams on fish migration and survival so that mitigation techniques can be applied to recover endangered populations (or to prevent endangerment in the first place). However, biologists are limited by the relatively large size of transmitters because of the potential to negatively impact and bias animal behavior. For example, the American Ornithologists' Union suggested that the transmitter weight should not exceed 5% of the body weight of birds. American Society of Mammologists recommend transmitter weight should be less than 5% of the bats' body weight. Miniature radio-frequency (RF) transmitters used for tracking small aquatic, airborne, or terrestrial animals/objects that may be injected are provided herein.